The field of the invention relates to providing operator initiated commands to a speed control system and decoding of those commands.
Various approaches are known to provide operator actuable switches and decoding of switch status for providing speed control commands or modes. Typically, actuation of the set switch causes vehicle speed to be stored as the reference speed at the time of actuation. Thereafter, a servo controls the engine throttle in response to a difference between vehicle speed and reference speed for maintaining vehicle speed at the reference speed. Continued actuation of an accel switch results in incrementation of the reference speed to provide vehicle acceleration during switch actuation. The set and accel switches may be the same switch and the speed controller would then distinguish between the set mode and accel mode by decoding switch actuation time.
Continuing with typical speed control commands, actuation of the vehicle brakes results in a standby mode wherein speed control operation is temporarily disabled. Speed control operation is subsequently restored at the previous reference speed upon actuation of a resume switch.
It is also known to provide a single multiplex output from all the operator actuable switches and decode various speed control commands from the single output as shown in Carp. U.S. Pat. No. 3,599,052. The '052 patent shows a number of operator actuable switches mounted on the steering wheel which communicate with the speed controller via a single line.
Speed controllers are also known which set an error flag when the vehicle brake is depressed concurrently with any of the speed control switches. Resumption of speed control operation is prevented when such error flag is in a set state. The error flag is then cleared when all speed control switches are detected as being in a neutral or idle state thereby enabling resumption of speed control operation upon actuation of the appropriate switch.
Suzuki et al U.S. Pat. No. 4,394,739 discloses a speed control system wherein control of the actuator (based upon a deviation between reference speed and vehicle speed) is disabled when the resume switch is toggled to the active position and subsequently enabled when the resume switch is toggled back to the inactive position. Another Suzuki patent (U.S. Pat. No. 4,451,890) resets the reference speed to zero when the resume switch is toggled on and the vehicle brakes are applied.
Suzuki et al U.S. Pat. No. 4,434,469 discloses an acceleration switch, which is independent of the set switch, and circuitry for disabling power to the accelerator circuitry when the brakes and accelerator switch are concurrently activated.
Frantz U.S. Pat. No. 4,890,231 discloses a speed control system in which a resume flag is set whenever the resume mode is entered. Subsequent resume operations are prevented if the resume flag remains set. The resume flag is cleared only after application of the vehicular brakes and verification that the resume switch is in the off state.
The inventors herein have recognized prior approaches teach specific decoding systems for a particular mode of operation. Combining such specific systems into an overall decoding system results in redundancy and added complexity.